
//岛屿数量

import java.util.LinkedList;
import java.util.Queue;

public class demo3 {
    int[] dx = {0,0,1,-1};
    int[] dy = {1,-1,0,0};
    int m,n;

    boolean[][] vis = new boolean[301][301];

        public int numIslands(char[][] grid) {
            int ret = 0;
            m = grid.length;n = grid[0].length;
            for (int i = 0; i < m; i++) {
                for (int j = 0; j < n; j++) {
                    if (grid[i][j] == '1' && !vis[i][j]){
                        ret++;
                        bfs(grid,i,j);
                    }
                }
            }
            return ret;
        }

    private  void bfs(char[][] grid, int i, int j) {
        Queue<int[]> q = new LinkedList<>();
        q.add(new int[]{i,j});
        vis[i][j] = true;
        while(!q.isEmpty()){
            int[] t = q.poll();
            int a = t[0],b =t[1];
            for (int k = 0; k < 4; k++) {
                int x = a+dx[k],y = b+dy[k];
                if (x >= 0 && x < m && y >= 0 && y < n
                        && grid[x][y] == '1' && !vis[x][y]){
                    q.add(new int[]{x,y});
                    vis[x][y] = true;
                }
            }
        }
    }
}
